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The purpose of this paper is to describe the methodology adopted to design an electric motor applied to the traction of a single-seat high-performance electric vehicle. A comparative selection of topologies of electrical machines is made and then, an analytical model of the chosen layout is described. An evolutionary algorithm is used in order to find an optimized solution according to some selected performance criteria. Afterwards, the analysis of the selected design is made in a finite element simulation software. Finally, a comparison between the analytical and the finite element models results is performed.

This paper presents a performance analysis of four topologies of permanent magnet synchronous generators (PMSG) generating power for a 3 kW, 220 V, three-phase, Y-connected resistive load, based on a methodology for the optimal design of PMSG using ferrite permanent magnets. The optimal designs of the machines, intended for small wind turbines, use multidisciplinary optimization models and a deterministic algorithm. As high power density is desired, only flux concentration topologies that allow high values of magnetic induction in the air gap were proposed, including inner and outer rotor machines. For the inner rotor conventional machines, both an integer and a fractional number of slots per pole per phase were proposed. A conventional and a vernier radial flux machine, both of them with outer rotor and fractional number of slots per pole per phase, were also considered. After validation of each optimal design by a finite element analysis software, the more convenient number of pole for each topology was identified, observing that the vernier machine presented the lowest torque ripple, the highest power density and the lowest active material cost among the four topologies of PMSGs.

The paper proposes a multidisciplinary design optimization (MDO) of permanent magnet synchronous generators (PMSG) for wind energy conversion systems (WECS). Such a MDO seeks the best compromise between the PMSG cost and the lifetime energy production of the WECS. So far, most of the papers in this field presented design methods using quite a few optimization variables and requiring a lot of assumptions. In the proposed MDO the specifications consist of geometrical, economical, magnetic, electrical and thermal constraints. Several analytic and semi-analytic sub-models where used to deal with these constraints, resulting in a large non-linear optimization problem that uses a sequential quadratic programming optimization algorithm. The paper considers the annual wind profile to estimate the lifetime wind turbine energy production. Moreover, the best possible solutions are presented in a Pareto front showing the trade-off between the generator cost and the wind turbine energy production. Among them, one optimal solution machine was chosen to be further investigated and its results were verified by finite element analysis.

International audience; The present paper deals with a large multidisciplinary design optimization (MDO) applied to a wind turbine permanent magnet synchronous generator (PMSG). The multidisciplinary nature of the model allows reliable results, but it demands high complexity and a large number of variables. Furthermore, to calculate the wind turbine energy production it is necessary to include several operating points in the model, increasing even more the dimension of the problem. To deal with this large optimization problem, the sequential quadratic programming (SQP) algorithm has been chosen. The results show that, besides the model complexity, the solution is obtained fast.

International audience; This paper presents the multiphysics design optimization of a permanent magnet synchronous generator (PMSG). A medium-power wind turbine (55 kW) is taken as the basis for the design optimization, whereas reducing its cost is the optimization goal. The design comprises the multiphysics generator model and the cost and losses models of the grid connection static power converters (SPC). The power converter command strategy is analyzed as it influences the system cost. Papers that dealt with the optimal design of the PMSGs usually did not consider the SPC cost and losses in the total system cost. The analysis of three power converter command strategies, implemented in the multidisciplinary design optimization, aims to define the phase angle of the generator current that leads to the lowest cost of the system composed by the generator and power converter.

This paper presents the analysis and the design of a ferrite permanent magnet synchronous generator (FePMSG) with flux concentration. Despite the well-known advantages of rare earth permanent magnet synchronous generators (REPMSG), the high cost of the rare earth permanent magnets represents an important drawback, particularly in competitive markets like the wind power. To reduce the cost of permanent magnet machines it is possible to replace the expensive rare earth materials by ferrite. Once ferrite has low remanent magnetization, flux concentration techniques are used to design a cheaper generator. The designed FePMSG is compared with a reference rare earth (NdFeB) permanent magnet synchronous generator (REPMSG), both with 3 kW, 220 V and 350 rpm. The results, validated with finite element analysis, show that the FePMSG can replace the REPMSG reducing significantly the active material cost.

The paper analyzes the performance of vernier synchronous generators as compared to synchronous generator, both with spoke ferrite permanent magnets and outer rotor. An existing wind turbine synchronous generator of 3 kW / 350 rpm with internal rotor and surface NdFeB permanent magnets was taken as a reference. A semi-analytical multiphysics design optimization methodology, employing a deterministic algorithm, was used to minimize the mass of generator active materials. Reluctances magnetic equivalent circuits were used to obtain the electromotive force and inductances. The results show that the vernier machine has a higher power density with less torque ripple and lower cost of active materials than the corresponding synchronous one. When compared to the NdFeB magnets reference machine, the vernier generator with spoke ferrite magnets has a significantly lower cost of active materials and a slightly higher power density. A finite elements software was used to validate the results.

A computer model, including analytical and FEM formulations, was developed to calculate the starting performance of synchronous motors with solid rotor salient poles. Using quasi-steady state equations, the average and the envelope of the oscillating electromagnetic torque as well as the stator rms current are calculated. With the stator current, the rotor pole losses are evaluated by FEM. The complete simulation process is performed by self-contained software composed by several computational modules properly tiled to simplify the work of a design engineer. The calculated starting performance was compared to experimental results showing satisfactory consistency.

Line-start permanent magnet motor (LSPMM) is a very attractive alternative to replace induction motors due to its very high efficiency and constant speed operation with load variations. However, designing this kind of hybrid motor is hard work and requires a good understanding of motor behavior. The calculation of load angle is an important step in motor design and can not be neglected. This paper uses the finite element method to show a simple methodology to calculate the load angle of a three-phase LSPMM combining the dynamic and steady-state simulations. The methodology is used to analyze a three-phase LSPMM.

This paper presents the multidisciplinary design optimization (MDO) of a WECS permanent magnet synchronous generator (PMSG). The MDO is applied to a medium power WECS (55 kW) with the objective of reducing its cost. The WECS model includes, in addition to the model of the PMSG, cost and losses models of the power converter. The wind turbine cost is not included in the model. Although numerous papers discuss the optimal design of the PMSG, few examine the influence of power converter cost and losses in WECS total cost. The optimal design methodology proposed here produced three different WECS, each to a different phase angle of the current. The results show that the current phase angle affects the costs of the PMSG and of the power converter differently. The result of the optimization allowed to define the phase angle of the current which minimizes the total cost of the WECS.

A new control of a grid connected permanent magnet synchronous generator (PMSG) for wind turbines based on the Instantaneous Power Theory (pq Theory) is proposed. Given the PMSG trapezoidal electromotive force (EMF), the proposed pq control is advantageous over those based on the Park transformation, because it reduces the electromagnetic torque ripple and eliminates the calculation of sinusoidal functions. It is simpler and efficient and well adapted to medium power wind turbines. Back-to-back voltage source converters with vector PWM modulation connect this generator to the grid. Synchronization and control of the power flow are based on the pq Theory with proportional-resonant current regulators on the grid-side, and proportional-integral current regulators on the generator-side. A trapezoidal EMF reference curve is generated as a function of the measured rotor position. The DC link voltage is controlled on the generator-side, ensuring its control even in the presence of symmetrical voltage sag at the grid connection. A wind turbine Maximum Power Point Traking (MPPT) strategy is also implemented. The complete system has been modeled in Matlab/Simulink. A test bench was constructed with a 3 kW PMSG. A wind turbine emulator was built to drive the PMSG emulating the characteristics of a wind turbine. Simulated and experimental results are presented that validate the proposed control strategy.

The paper shows the results of an optimization strategy that takes into account the annual wind profile of a wind turbine to design a high-efficiency permanent magnet synchronous generator. The energy yield is considered in the optimization method by including the cost of losses in the objective function, which is the sum of the costs of losses, active materials and structure. The optimally designed machine is a 3-phase permanent magnet synchronous generator with 48 poles and 40 kW for direct drive wind turbines. To show the advantages of employing the proposed strategy, the results of a standard optimization strategy, which minimizes the generator costs not regarding energy production, are also presented and compared. It is shown that the difference in energy proceeds is sufficient to compensate the higher cost of the high-efficiency generator. At the end the trade-off between the PMSG efficiency and its cost is analyzed using a Pareto front.

A new control of a grid connected permanent magnet synchronous generator (PMSG) for wind turbines based on the Instantaneous Power Theory (pq Theory) is proposed. Given the PMSG trapezoidal electromotive force (EMF), the proposed pq control is advantageous over those based on the Park transformation, because it reduces the electromagnetic torque ripple and eliminates the calculation of sinusoidal functions. It is simpler and efficient and well adapted to medium power wind turbines. Back-to-back voltage source converters with space vector PWM modulation connect this generator to the grid. A trapezoidal EMF reference curve is generated as a function of the measured rotor position. The DC link voltage is controlled at the generator side, ensuring its control even in the presence of asymmetrical voltage sag at the grid connection. A wind turbine maximum turbine power point (MTPP) following strategy is also implemented. The complete system has been modeled in Matlab/Simulink. A test bench was build with a 3 kW PMSG that included a wind turbine emulator to drive the PMSG. Simulated and experimental results are presented that validate the proposed control strategy.

This paper shows the results of an optimization strategy that takes into account the annual wind profile of a wind turbine to minimize the generator cost and maximize the energy yield. The optimally designed machine is a 3-phase permanent magnet synchronous generator with 48 poles and 30 kW for direct drive wind turbines. The energy yield is considered in the optimization method by including the cost of losses in the objective function, which is then the sum of cost of losses, cost of materials and structure costs. To show the advantages of employing this strategy, the results of a standard optimization strategy, which minimizes the generator costs not regarding energy production, are also presented and compared. It is shown that this strategy results in a machine that produces more energy during its lifetime, which compensates its higher cost. Finite element analysis software is used to verify and validate the resulting machine.

A model allowing the simulation of induction machines with different rotor bars configurations is presented. The electrical machine is modeled by using two-dimensional (2-D) finite-element method and its equations are directly coupled with those of the circuit. A general and new contribution is added for the consideration of special rotor bars topologies. The movement is taken into account by means of the moving band technique, the Maxwell stress tensor, and the mechanical oscillation equation. The model is applied to a brushless doubly fed induction motor.

This work uses a method based on the two-dimensional (2-D) finite-element method (FEM) and on the circuits theory to model the interbar currents in a skewed cage induction motor. With this model, the effects of the stator-slot opening on interbar currents are analyzed. Two values of the stator-slot width are considered. The skewing effect is taken into account by the multislice technique.

A methodology allowing one to include iron losses in voltage fed time stepping finite elements simulations is presented in this paper. Hysteresis, eddy currents and anomalous losses models are introduced in the 2D field formulation based on the magnetic vector potential. The influence of the losses on the behavior of an Epstein frame is given. Comparison between simulated and measured results shows the validity of the proposed methodology.

This paper deals with the coupling between magnetic forces, forced vibrations and noise in a Switched Reluctance motor. The finite element method is used to obtain the magnetic forces and forced vibrations. The boundary element method is used for acoustic computations.

This work presents an improved method to take into account the magnetic nonlinearity in time-stepped two dimensional finite element calculations. A differential magnetic reluctivity tensor is employed. Also, in order to model the nonlinearity, a Langevin function is used. Numerical convergence is faster than classical procedures.

This work presents a new methodology for determination of hysteresis curves based on the Jiles–Atherton method. The magnetic induction is adopted as an independent variable which is available in the vector potential magnetic field formulation. The presented method can be directly incorporated in a finite element software.

In this paper, a finite element model is used to investigate the squirrel cage induction motor vibrational behavior. This model allows to calculate the winding and bar currents, the magnetic forces and motor structure dynamic response. The vibrations and magnetic forces are obtained by numerical calculations and validated by measurements.

This paper presents the implementation of the control loop in the simulation of the association converter/electromagnetic structure represented by two-dimensional finite element method. The state variable equations of the converter are constructed entirely in an automatic manner. These equations are then coupled to the electromagnetic structure equations, and finally solved simultaneously using time stepping procedure. In order to validate the proposed method, a simulation of an inverter connected to an electromagnetic structure including an hysteresis current control scheme is performed.

Numerical and experimental procedures are presented in this work in order to study the vibration behavior of switched reluctance motors (SRM). Experimental modal analysis and finite element methods (FEM) are used to determine the mode shapes and natural frequencies of the motor mechanical structure. The forces acting on the stator are evaluated by means of a local force density method. The results show that a 2D model is sufficient for analyzing mechanical vibrations in SRM created by electromagnetic phenomena.

International audience; The optimal design of a set of two permanent magnet generators that share the same cross section to reduce the manufacturing cost is presented using a gradient optimization algorithm. The optimization tool is used to define the optimal number of pole pairs of the set of machines and the optimal permanent magnets width respecting the geometrical and performance constraints. The design is validated using a FEM analysis tool.

The permanent magnet synchronous generators (PMSG) used in wind turbines usually are machines with trapezoidal electromotive force (EMF) waveforms. The “instantaneous active and reactive power” theory is used to control the nonsinusoidal EMF permanent magnet generator. The objective is to reduce fluctuations of the generator's torque and power, and this was demonstrated in a previous paper by comparison with the traditional dq control. The grid-side converter control uses the dq technique, since the network voltages are sinusoidal. The low voltage ride through (LVRT) requirements are considered in the design of both the generator side and grid side converter control in the case of asymmetrical faults. The generator-side converter is responsible for maintaining constant the DC link voltage and not to the network side converter as usual. Simulations using Matlab/Simulink show the effectiveness of the techniques proposed here in two cases: one where the wind turbine experiences a step increase in the wind speed and the other when asymmetrical voltage sag occur at the network connection terminals.

The permanent magnet synchronous generators (PMSG) used in wind turbines usually are machines with trapezoidal electromotive force (EMF) waveforms. The control techniques based on Park's transformation, decomposing the voltages and currents into d and q axes, are not fully satisfactory when applied to such machines. For this reason, this paper proposes to realize the control of a permanent magnet generator with nonsinusoidal EMF using the “pq” or “instantaneous active and reactive power” theory. The objective is to reduce fluctuations of the generator's torque and power, and this is done by comparison between the dq and the pq control. On the other hand, the grid-side converter control is still done using the dq technique. The low voltage ride through (LVRT) requirements is considered in the design of the generator control on the case of symmetrical faults. A control technique is used in which the responsibility of maintaining the DC link voltage constant belongs to the generator-side converter and not to the network side converter as usual. Simulations using Matlab/Simulink show the effectiveness of the techniques proposed here in two cases: one where the wind turbine experiences a step increase in the wind speed and the other when a symmetrical voltage sag occurs at the network connection terminals.

The centrifugal casting process is a recognized technology that improves the quality and efficiency of induction motors and was largely used in the past in large integral horsepower motors. Recently this process caught the attention of small induction motors manufacturers and was implemented by some manufacturers of hermetic compressors for domestic refrigeration. Although some benefits of the centrifugal casting process are the same in small and large induction motors, there is one important contribution that is more pronounced in single-phase motors without run capacitors and it will be discussed in this paper. This work presents information of centrifugal casting process and experimental results obtained with induction motors with and without run capacitor.

A newly designed linear actuator using permanent magnets is analyzed. In order to evaluate its dynamic performance, the coupling between electromagnetic equations is established. Due to the different phenomena involved, analytical procedures cannot provide reliable results. Thus the magnetic forces and other quantities are obtained by 2D and 3D calculations. In order to obtain the 3D field values, edge elements are used; with this type of finite elements, modeling taking into account the permanent magnets is also introduced.

International audience; A method to model the switched reluctance motor is presented in this paper. The methodology is based on the simultaneous solution of the magnetic field, represented by the two dimensional Finite Element Method, with electrical circuit equations. With this model the currents in the windings are calculated and the force distribution on the stator teeth is obtained. The mechanical response to magnetic forces is calculated by a Finite Element code

A general method for coupling field and electrical circuit equations is presented in this work. The external electrical equations associated with the feeding circuit are represented in state space form. To illustrate the proposed methodology the dynamical operation of a single-phase induction motor is carried out. >

This paper presents a Wind Turbine Emulator (WTE) with induction motor driven by scalar torque control inverter. Additionally, the closed loop torque and rotor flux was implemented so that the induction motor emulates the real behavior of the wind turbine. The wind turbine model is developed considering its aerodynamics characteristic. This model will define the torque level in the electrical generator shaft. The induction motor control system implemented is capable to regulate the electromagnetic torque and rotor flux independently. The simulated results demonstrate the effectiveness of the induction motor system control. The strategy control was implemented in simulation using Matlab/Simulink/SimpowerSystems.

This paper is a methodological contribution in order to characterize two kinds of models that should be used in a complete optimization process of energy conversion systems like motors or actuators. We will indeed introduce the concept of "sizing model", and the concept of "optimization model". We will show also how to use them in a design process in order to produce optimal result that we concatenate in “an optimal design graph”. All those methodological results will be illustrated on the optimal design of a Permanent Magnet Generator (PMG).

International legislation demanding high efficiency motors is the great challenge facing motor manufacturers. The use of new topologies, materials and processes are the key to have motors accepted in the market. The use of fully processed steel has increased considerably in the last few years due to its competitive price and better magnetic properties. With lower losses and/or higher permeability, this steel allows a considerable improvement of motor efficiency. However its use requires a good understanding of its mechanical, electrical and magnetic properties. This works presents the results of simulation and tests obtained from small motors for refrigeration using different fully processed steels. Results show that, under some conditions, the use of fully processed steel may lead to motors having the same efficiency as those using the semi-processed steel. Additionally, the annealing sometimes neglected by some manufacturers, requires some care when aluminum is in the steel composition.

Single-phase induction motor (SPIM) has been widely used in home appliances due to its simplicity, low cost, low noise and ruggedness. However, to produce a cost effective high efficiency SPIM is necessary to have a good knowledge and good control of process parameters. Dynamometer's results of motors made with different process parameters show that rotor cages are more sensitive to process variations than stators and that they can to worsen the motor efficiency and torque characteristics. The aim of this work is to evaluate some steps of rotor cage process, namely rotor laminates coating, aluminum die-cast methods and rotor annealing and to analyze the effect of such parameters on motor performance. Results obtained from tests with a 2-pole, 100 W, high-efficiency SPIM are presented.

Generator air gap non-uniformity causes an imbalance of magnetic forces that result in Unbalanced Magnetic Pull - UMP. This phenomenon can cause high vibrations on the rotor. The addition of equipotential connections leads to an increment of the circulating current among parallel circuits of the stator winding, decreasing the magnetomotive force of armature reaction. Since the forces of magnetic attraction are proportional to the square of the resulting air gap magnetic induction, a change in their values along the circumference of the rotor, with the help of equipotential connections, will reduce the UMP. This solution is economically advantageous and the machine stop time can be shortened.

Cogging torque is produced in a permanent magnet machine by magnetic attraction between the rotor permanent magnets and the stator teeth. It is an undesirable effect that contributes to torque ripple, vibration and noise of the machine. In this paper, the resultant cogging torque values are computed using a three-dimensional (3D) finite element analysis. For this, the rotor movement is modeled by means of the moving band technique in which a dynamic allocation of periodic or anti-periodic boundary conditions is performed. The 3D finite element method is the most accurate tool to carry out cogging torque. However, it does not easily allow a parametric study. For this reason, an analytical model was developed in order to predict the cogging torque. The tools are intended to be used for the study of transverse flux machines.

This paper presents a mathematical model of a three-phase induction motor taking into consideration the interbar contacts. Several models have been available in the references. However, they consider the rotor of the induction motor as being constituted either a three-phase or a squirrel cage even if it operates under stator and/or rotor faults condition. Nonetheless, the contact between a bar and the iron core for the machine has to be considered, especially when a rotor fault occurs. It is obvious that rotor currents are under the influence of rotor constitution materials. So, the paper aim’s concerns a transient model of the induction motors which can consider the rotor broken bars defect. Despite its increasing complexity, it could be able to provide with useful indications for diagnostic purposes. This model is advocated for the simulation of motors behavior under rotor defect which takes into account the interbar currents. The proposed technique is based on the mesh model analysis of the squirrel cage. As low power induction motors are prevalent in industrial plants, we pay a special attention on them. Notwithstanding, additional currents are due to the contact between the non-insulated bar constituting the squirrel cage to the rotor iron core. The monitoring of induction motors is predominantly made through the stator current analysis of the motor when it operates at nominal condition. Moreover, this one is observed in steady state operating system, knowing that the motor is generally fed by a sinusoidal supply. Consequently, simulation results showed in this paper prove the effectiveness of the proposed approach, and the impact of interbar resistance both on the model and the line current spectrum for the diagnostic. An experimental test proves the effectiveness of this model.

The eh-star method is a procedure proposed in the IEC 60034-2-1 standard to determine the stray load losses in three-phase induction motors. In this test, the motor is fed by an unbalanced supply, which is obtained using an electrical resistance (Reh) in parallel with two phases of the star-connected motor and a single-phase source. The purpose of this paper is to present a new calculation routine that determines the stray load losses from eh-star test data. This routine is obtained from an electrical circuit, in which the unbalanced supply results from two phases and the neutral of the generator, eliminating Reh. The results show that the proposed method presents good agreement with the conventional eh-star method.

In some electrical equipment it can be useful to calculate the currents and temperatures caused by Joule effects in critical regions, especially when high voltages are present and high current densities are applied. In the present work, a 2-D finite-element method is presented whose goal is to determine the evolution of currents and temperatures with time for this kind of situation. Specifically, the authors present a methodology for evaluation of currents and temperatures in a coupled-transient problem, using the electrical vector potential. Experimental results were obtained in a switchgear where the contact region is quite similar to the domain presented here. The agreement between the experiment and the proposed method is good. >